Climate change causing historic drought

Not only is the changing climate a contributing factor to the current drought, but with the current effects and future outlook for dry weather, conditions are forecast to intensify as a result of higher temperatures caused by the warming climate.

In spite of political disagreements and the controversy associated with climate change, four university experts staged an online press conference last week to highlight their conclusions connecting drought to climate change as compiled in the recent National Climate Assessment Southwest Report.

According to that report, not only is the changing climate a contributing factor to the current drought, but with the current effects and future outlook for dry weather, conditions are forecast to intensify as a result of higher temperatures caused by the warming climate.

Assessment of Climate Change in the Southwest United States is one of a series of regional reports prepared for the 2013 National Climate Assessment. It is a landmark study in terms of its breadth and depth of coverage.

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The report is coordinated by the Southwest Climate Alliance, a consortium of researchers affiliated with the NOAA Regional Integrated Sciences and Assessments in the Southwest, specifically, the California–Nevada Applications Program, Climate Assessment for the Southwest, Western Water Assessment and the Department of the Interior Southwest Climate Science Center.

The report blends the contributions of 120 experts in climate science, economics, ecology, engineering, geography, hydrology, planning, resource management, and other disciplines to provide the most comprehensive and understandable, analysis to date about climate and its effects on the people and landscapes of the Southwest.

During last week's press conference, scientists and economists from Nevada, California, Kansas and Arizona stressed the importance of recognizing the drought’s connection to climate change, particularly its implications for local water supplies, agricultural productivity and long-term changes in land use across the West and Southwest. Without exception, each of the participating scientists agreed that higher average temperatures caused by a warming climate are making the current drought a record-breaking event.

"Western and Southwestern states are feeling the effects of reduced water supply, and these are the types of scenarios expected under climate change conditions," said Dr. Thomas Piechota, Interim Vice President for Research, University of Nevada, Las Vegas, and lead author on the National Climate Assessment Southwest report. "Nevada now has clear indications of drought, and this extends to varying extents to the Colorado River basin and across the region. These are the type of conditions that the National Climate Assessment report characterized, and as snowpack and streamflow amounts continue to decline we will see decreased water supply for cities, agriculture and ecosystems."

Nearly 97 percent of Nevada is experiencing drought, with nine counties in Nevada declared disaster areas. The federal government has declared parts of 10 other western and central states as natural disaster areas because of the drought: California, Arizona, Kansas, Texas, Utah, Arkansas, Hawaii, Idaho, Oklahoma and Colorado. Oregon, while not in the 11-state region of drought emergencies, also has severe drought conditions.

Part of a trend

Dr. John Harrington Jr., Professor of Geography, Kansas State University, said the western portion of Kansas is now experiencing severe drought of exactly the type expected from a changing climate.

"What’s happening in Kansas is part of a much larger trend. The climate system has fundamentally changed, with human-driven emissions permanently altering temperatures and precipitation patterns. Droughts like this will continue and get worse until climate change is addressed,” he said.

In Kansas, nearly half (47 percent), of the state remains in drought, including 37 counties, according to the U.S. Drought Monitor. The winter wheat crop in particular is at risk from dry weather and rapid weather swings.

“What we are seeing now is fundamentally different from previous mega-droughts, which were driven largely by precipitation. Now, thanks to higher temperatures driven by climate change, droughts are increasingly temperature-driven, which makes even normal levels of precipitation less effective in relieving drought conditions," added Dr. Valerie Trouet, Assistant Professor in the Laboratory of Tree-Ring Research, University of Arizona.

She added that the current conditions of severe drought in the West/Southwest and bitter cold, ice and snow in the East and Southeast are related to the impact of global warming on the jet stream. With more warming, the jet stream is slowing down, she claimed. She says the polar vortex is the flip side of the California drought.

According to the U.S. Drought Monitor, at least moderate drought conditions currently cover 60 to 80 percent of both Arizona and New Mexico, resulting in extreme wildfire outbreaks across the region.

The experts emphasized that the drought is likely just the latest in a series of worsening extreme conditions in the West. They noted that the Southwest has heated up markedly in recent decades, and the period since 1950 has been hotter than any period of the same length in at least 600 years.

Dr. Michael Hanemann, Professor of the Graduate School, Department of Agricultural & Resource Economics, University of California, Berkeley, noted the California drought is already as bad as or worse than any drought in recent memory, and "likely the worst the state has seen in seventy years.

"In previous droughts, Mother Nature has had no more than two dry winters in a row. We have now had two dry winters, but there is no guarantee that next winter will be wet. In fact, climate change makes it far more likely that we will have an unprecedented third dry winter. The implications of that for California’s water supplies, agriculture and people would be alarming to say the least,” he said.

This report is designed to offer decision makers and stakeholders a substantial basis from which to make informed choices that will affect the well-being of the region’s inhabitants in the decades to come.